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Don't bother comparing constructor when deps are not provided #14594

Merged
merged 3 commits into from
Jan 17, 2019
Merged

Don't bother comparing constructor when deps are not provided #14594

merged 3 commits into from
Jan 17, 2019

Commits on Jan 17, 2019

  1. Don't bother comparing constructor when deps are not provided 

    When no dependencies are passed to an effect hook, what we used to do is
compare the effect constructor. If there was no change, then we would
skip firing the effect. In practice, this is a useless optimization
because the constructor will always be different when you pass an inline
closure. And if you don't pass an inline closure, then you can't access
any props or state.

There are some edge cases where an effect that doesn't close over props
or state could be useful, like reference counting the number of mounted
components. But those are rare and can be addressed by passing an empty
array of dependencies.

By removing this "optimization," we can avoid retaining the constructor
in the majority of cases where it's a closure that changes on
every render.

I made corresponding changes to the other hooks that accept
dependencies, too (useMemo, useCallback, and useImperativeHandle).
    @acdlite
    acdlite committed Jan 17, 2019
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  2. Improve hook dependencies warning 

    It now includes the name of the hook in the message.
    @acdlite
    acdlite committed Jan 17, 2019
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  3. Nits

    @acdlite
    acdlite committed Jan 17, 2019
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